Irrigated Agricultural Areas Research Articles

An Analysis of Influences of Interbasin Water Transfer on Water Resources Carrying Capacity Over Dianchi-Pudu River Basin

This paper adopts the maximum carrying population, industrial added value and agricultural irrigation area to develop a multi-objective model of water resources carrying capacity (WRCC) in Dianchi-Pudu river basin. The model is used to calculate the WRCC for Dianchi-Pudu river basin in 2020 and 2030 respectively in terms of three different water supply schemes. Results show that except Scheme III which can basically support future socio-economic development and population increase, both Scheme I and II cannot support future socio-economic development and population increase of Dianchi-Pudu river basin. Interbasin water transfer would greatly increase the WRCC of Dianchi-Pudu river basin while efficient water saving can merely work in a limited extent. Consequently, interbasin water transfer and efficient water-saving are the necessaries to guarantee the positive balance between the exploitation of water resource and socio-economic development of Dianchi-Pudu river basin.

A novel regional irrigation water productivity model coupling irrigation- and drainage-driven soil hydrology and salinity dynamics and shallow groundwater movement in arid regions in China

Abstract. The temporal and spatial distributions of regional irrigation water productivity (RIWP) are crucial for making decisions related to agriculture, especially in arid irrigated areas with complex cropping patterns. Thus, in this study, we developed a new RIWP model for an irrigated agricultural area with complex cropping patterns. The model couples the irrigation- and drainage-driven soil water and salinity dynamics and shallow groundwater movement in order to quantify the temporal and spatial distributions of the target hydrological and biophysical variables. We divided the study area into 1 km × 1 km hydrological response units (HRUs). In each HRU, we considered four land use types: sunflower fields, wheat fields, maize fields, and uncultivated lands (bare soil). We coupled the regional soil hydrological processes and groundwater flow by taking a weighted average of the water exchange between unsaturated soil and groundwater under different land use types. The RIWP model was calibrated and validated using 8 years of hydrological variables obtained from regional observation sites in a typical arid irrigation area in North China, the Hetao Irrigation District. The model simulated soil moisture and salinity reasonably well as well as groundwater table depths and salinity. However, overestimations of groundwater discharge were detected in both the calibration and validation due to the assumption of well-operated drainage ditch conditions; regional evapotranspiration (ET) was reasonably estimated, whereas ET in the uncultivated area was slightly underestimated in the RIWP model. A sensitivity analysis indicated that the soil evaporation coefficient and the specific yield were the key parameters for the RIWP simulation. The results showed that the RIWP decreased from maize to sunflower to wheat from 2006 to 2013. It was also found that the maximum RIWP was reached when the groundwater table depth was between 2 and 4 m, regardless of the irrigation water depth applied. This implies the importance of groundwater table control on the RIWP. Overall, our distributed RIWP model can effectively simulate the temporal and spatial distribution of the RIWP and provide critical water allocation suggestions for decision-makers.

RETRACTED ARTICLE: Monitoring soil salinization in Manas River Basin, Northwestern China based on multi-spectral index group

ABSTRACT Large-scale and accurate monitoring soil salinization is essential for controlling soil degradation and sustainable agricultural development. The agricultural irrigation area of the Manas River Basin in the arid area of Northwest China was selected as the test area. The soil salinization monitoring model based on spectral index group was constructed by comparing the accuracy of PCR, PLSR and MLR models using the transformation of multi-spectral index group and index screening. The results showed that there was a certain correlation between the 28 spectral index groups, with a maximum correlation coefficient -0.3689 between the original spectral group and the soil salt content was B10 band. After the transformation of original data for the logarithm Ln(R), exponential eR and square root R1/2 respectively, the correlation between each index and soil salinity was significantly improved, with the maximum correlation coefficient was up to -0.7564 of R1/2. The salt content estimation models were constructed by different data transformation using PLSR, PCR and MLR methods, respectively. This study provides a fast and accurate method for monitoring regional soil salinity content and the results can provide a reference for soil salinity grading management in arid and semi-arid areas.

Variation and driving mechanism analysis of water footprint efficiency in crop cultivation in China

Water footprint regulation in agricultural production is of great significance to regional food, water and ecological sustainability. The spatial-temporal characteristics and driving mechanism of water footprint efficiency (WFE) in crop cultivation in China during 1996–2015 were analysed based on the quantification of the crop-water relationship. The results showed that China's total crop water footprint (TWF) was 1125.6 G m3, and the blue, green and grey components accounted for 24.4%, 57.4% and 18.2%, respectively. The national WFE was 0.681 and increased over time due to the improvement of agricultural technology. Spatial autocorrelation analysis showed that provinces with similar WFE values were clustered geographically and have gradually weakened since 2012. Provinces with a high WFE were concentrated in the southeast and northeast, and low-value provinces were distributed in the west of China. The main anthropogenic driving factors were the preliminary fertilizer application intensity (FAI) and population density (PD); however, these factors have been replaced by the irrigation efficiency (IE), agricultural water use ratio (AWR) and irrigation area proportion (IAP) in recent years. Specific regions should formulate water resource management policies according to their WFE performance, agricultural production scale and water resource endowment. The northeast should control crop cultivation and enhance the yield to solve water shortage problems, the central provinces should improve WFE, and the southern provinces should contribute to the promotion of national water use efficiency by expanding crop sowing and irrigation areas. This study provides a reference for water resource management in the context of social and environmental change.

An Agricultural Interval Two-Stage Fuzzy Differential Water Price Model (ITS-DWPM) for Initial Water Rights Allocation in Hulin, China

In recent years, China’s agricultural water consumption has been high, while water inefficiency has restricted the development of the economy. In this study, we developed an agricultural interval two-stage fuzzy differential water prices model (ITS-DWPM) by incorporating the techniques of two-stage programming (TP) and interval-parameter programming (IPP) based on the differential water price. The ITS-DWPM can link the associated economic penalty attributed to the violation of the preregulated water target and the total system benefit under limited data availabilities (expressed stochastic and interval values); meanwhile, inaccurate water quantity data and dynamic economic data would be resolved. The methodology tended to resolve the complexity of initial water rights allocation problems, incorporating the relevant sectors as well as the agricultural irrigation system construction involved in water management decision. Furthermore, the model takes into account the restrictions on water quantity and price. In addition, multiple decision results were calculated under different states of water shortage. The developed method is applied to initial water rights allocation and agricultural irrigation system construction. The results generated can assist decision makers not only in formulating water rights allocation strategies, but also in balancing the contradiction between economic objectives and water resources control indicators. In 2020, the irrigation water utilization coefficient of each agricultural irrigation area in Hulin City should reach 0.55. Hutou needs to increase its agricultural irrigation channels by at least 4.49%, Shitouhe by at least 4.03%, and Daxinancha by at least 4.49%.

New perspective about application of extended Budyko formula in arid irrigation district with shallow groundwater

Budyko’s treatment of the long-term water balance of watersheds was based on the competition between water availability and energy supply. It assumes, in the long-term, that precipitation is the only source of water availability for evapotranspiration while the changes in soil water storage are negligible. For arid irrigation areas with shallow water tables, however, groundwater also can supply crop water demand in addition to irrigation and precipitation. In this study, we present a new Budyko formula considering seasonal groundwater uptake and soil water storage changes estimated by Aver’yanov’s equation and abcd model, respectively. The use of groundwater depths rather than the variation of groundwater levels makes it more reasonable to estimate seasonal groundwater consumption. For the application of the Budyko equation in unsteady state areas, equivalent precipitation was designed to take the place of precipitation as water availability. With the newly defined water availability, the relationship between evapotranspiration ratio and aridity index was described successfully by Budyko curves, otherwise the points exceeded Budyko domain with only precipitation and irrigation considered. Furthermore, for agricultural irrigation areas, the variation of seasonal ω is supposed to be affected by vegetation coverage (denoted by NDVI). Overall, it is possible to estimate regional actual seasonal and annual evapotranspiration for irrigation areas with shallow groundwater using the extended Budyko models. This new method can play significant role in water management in arid and semiarid agricultural regions.

Water Price Calculations in Concept Of Environmental Service: A Case in Cimanuk Watershed

Cimanuk Watershed is one of the important water sources in West Java Province. The damage that occurred in Cimanuk watershed affected the sustainability of water supply in West Java. The administrative area of ​​Cimanuk watershed extends to 4 regencies, namely Garut Regency, Sumedang Regency, Majalengka Regency, and Indramayu Regency. The Cimanuk River itself has a length of ± 338 km which can supply water needs of 2.2 billion m3 every year with the main utilization for irrigation in agricultural areas. Forest areas in the upper Cimanuk watershed affect the continuity of the hydrological, erosion and sedimentation process. Changes in the upstream area in terms of land use and forest exploitation that do not consider environmental aspects can damage the entire watershed ecosystem, causing fluctuations in water flow, sediment transport, and material dissolved in the water flow system. Given the reciprocal relationship in the concept of watershed management, the implementation of the Payment Environmental Services or PES mechanism is important, where water is one of components that deserves be consideration. The economic valuation of water quantified as water prices is also a fundamental reason for the importance of PES studies. Water prices based on scientific calculations, both qualitative and quantitative, determine the feasibility value that will be given from the downstream community upstream as conservation actors to support the concept of fair environmental services. Quantitative analysis is carried out in the form of valuations involving several methods, namely the Contingent Valuation Method, Value of Marginal Product Water, and Full Cost Pricing. The price of water can be used as an indicator of the cost of forest environmental services as a water provider as well as improving market mechanisms. This paper concludes the mechanism of payment for environmental services (PES) through water pricing policies can be an alternative source of funding to improve the condition of a watershed

Assessment of Lake Water Quality and Eutrophication Risk in an Agricultural Irrigation Area: A Case Study of the Chagan Lake in Northeast China

Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan Lake) in Northeast China. The hydro-chemical properties of the Chagan Lake are HCO3·CO3-Na. Nutrient (N and P) and non-nutrient (pH and F−) were found to be the major factors that threaten water quality safety of the lake. The concentration of total nitrogen (TN) and total phosphorus (TP) was found to vary seasonally and at different locations. The overall lake water had mean TN and TP values of 2.19 mg/L and 0.49 mg/L, respectively, in summer. TN was the major factor for water quality deterioration in the western region of the lake, while TP was the principal factor in the other regions, as determined by a principal component analysis (PCA). Fluoride (F−) concentration in the lake water were related to the values of total dissolved solid (TDS), pH, and electrical conductivity (EC). In addition, eutrophication is a fundamental index that has been affecting the ecological evaluation of water quality. The results showed that trophic level index (TLI), trophic state index (TSI), and eutrophication index (EI) were evaluated to quantify the risk of eutrophication. However, TLI and TSI can better describe the purification effect of the wetland. These indices showed that the lake water was hyper-eutrophic in summer, with TLI, TSI, and EI values of 60.1, 63.0, and 66.6, respectively. Disparities in water quality were observed among whole areas of the lake. Overall, this study revealed that controlling agriculture drainage is crucial for lake water quality management. The study generated critical data for making water quality management plans to control the risk.

Increasing Groundwater Availability and Seasonal Base Flow Through Agricultural Managed Aquifer Recharge in an Irrigated Basin

AbstractGroundwater aquifers provide an important “insurance” against climate variability. Due to prolonged droughts and/or irrigation demands, groundwater exploitation results in significant groundwater storage depletion. Managed aquifer recharge (MAR) is a promising management practice that intentionally places or retains more water in groundwater aquifers than would otherwise naturally occur. In this study, we examine the possibility of using large irrigated agricultural areas as potential MAR locations (Ag‐MAR). Using the California Central Valley Groundwater‐Surface Water Simulation Model we tested four different agricultural recharge land distributions, two streamflow diversion locations, eight recharge target amounts, and five recharge timings. These scenarios allowed a systematic evaluation of Ag‐MAR on changes in regional, long‐term groundwater storage, streamflow, and groundwater levels. The results show that overall availability of stream water for recharge is critical for Ag‐MAR systems. If stream water availability is limited, longer recharge periods at lower diversion rates allow diverting larger volumes and more efficient recharge compared to shorter diversion periods with higher rates. The recharged stream water increases both groundwater storage and net groundwater contributions to streamflow. During the first decades of Ag‐MAR operation, the diverted water contributed mainly to groundwater storage. After 80 years of Ag‐MAR operation about 34% of the overall diverted water remained in groundwater storage while 66% discharged back to streams, enhancing base flow during months with no recharge diversions. Groundwater level rise is shown to vary with the spatial and temporal distribution of Ag‐MAR. Overall, Ag‐MAR is shown to provide long‐term benefits for water availability, in groundwater and in streams.

Ecological and Economic Sustainability in Olive Groves with Different Irrigation Management and Levels of Erosion: A Case Study

In the last 50 years, both the agricultural labour force and irrigated land area have increased almost eightfold in Spain. The main objective of irrigation, in the short term, is to increase agricultural production. However, in the long term, the environmental externalities of irrigation and its direct relationship with soil erosion processes are more uncertain and still poorly studied. In this study, in an olive-growing region of Andalusia, Spain, the variation of several soil parameters related to irrigation and erosion levels was analysed. The results showed that irrigation, while increasing the productive level of the olive groves, entails a progressive alteration of the soil, modifying physical aspects (greater compaction and humidity of the soil together with lower gravel content, porosity and soil weight) and chemical aspects (reduction of the organic matter of the soil and the content of nitrates) that can aggravate the consequences of the erosive processes. In the long term, the productive benefit attributed to irrigation could be unsustainable from an ecological and, consequently, economic point of view. In addition, the lack of sustainability of olive irrigation agroecosystems could be exacerbated by the future restrictive impacts of climate change on water resources in Mediterranean environments. This situation demands spatial planning and alternative management based on soil conservation and rational and efficient forms of irrigation to ensure the sustainability of olive groves and their economic viability.

Triggering Influence of Seasonal Agricultural Irrigation on Shallow Loess Landslides on the South Jingyang Plateau, China

Since large-scale agricultural irrigation began in the 1980s, 92 landslides have occurred around the South Jingyang Plateau during the past 40 years. The geological disaster and soil erosion have caused numerous casualties and substantial property loss. In this work, several field investigations are carried out to explore the soil erosion and mechanical mechanism of these irrigated shallow loess landslides on the South Jingyang Plateau. (1) We investigated the spatial distributions, types and developmental characteristics of loess landslides. (2) We surveyed and monitored seasonal agricultural irrigation features and groundwater changes in the area since the 1980s and found that irrigation is a significant factor influencing groundwater changes, soil erosion and even causing landslides to occur. (3) Based on the field investigation, the occurrence of these irrigated shallow loess landslides was generalized, and it was found that the core process was due to the liquefaction of softening zone. We carried out a static liquefaction test and verified that the natural loess was prone to liquefaction. (4) The three main reasons for shallow loess landslides in the South Jingyang Plateau were discussed. This study provides a valuable reference for achieving an understanding of the relationship between seasonal agricultural irrigation and the occurrence of loess landslides in the area as well as similar irrigated agricultural areas.

Influence of Land Use and Land Cover on Hydraulic and Physical Soil Properties at the Cerrado Agricultural Frontier

Western Bahia is one of the most active agricultural frontiers in the world, which raises concern about its natural resources conservation, especially regarding water availability. This study evaluated the influence of five different land uses and land covers on physical and hydraulic soil properties, and developed pedotransfer functions to derive regional hydraulic properties. Significant changes between physical and hydraulic soil properties under agricultural areas and under natural vegetation cover were found, reinforcing that agricultural activity may influence the soil water balance. Cerrado and Forest formation areas have higher infiltration rates ( K s a t ) compared to managed areas, with average values of 16.29 cm h−1, and 14.47 cm h−1, while irrigated croplands, rainfed croplands and pasture areas have much smaller infiltration rates, with K s a t equal to 3.01 cm h−1, 6.22 cm h−1 and 5.01 cm h−1, respectively. Our results suggest that the agriculture practices do not directly affect the vertical nature of hydrological flowpath, except in the case of intensive irrigated agriculture areas, where K s a t reduction can lead to erosive processes favoring organic matter losses, and decreases in productivity and soil quality. Impacts of land use change on hydraulic and physical soil properties are a reality in the Cerrado agriculture frontier and there is an urgent need to monitor how these changes occur over time to develop effective mitigation strategies of soil and water conservation.

Impact of Resource Conserving Technologies (RCT) on soil physical properties and rapeseed (Brassica napus L.) yield in irrigated agriculture areas of the South-Eastern Kazakhstan

The aim of this resarch was to determine the effects of Resource Conserving Technologies (RCT) system and Conventional Tillage (CT) on soil physical properties and R apeseed ( Brassica napus L.) yield in irrigated agriculture areas of the South-Eastern Kazakhstan. The experimental study was conducted according to a radomized block design with three replications between 2015 and 2018. The CT system had maximum anthropogenic effect and caused loosening of arable soil layer, had the lowest bulk density values (1.19 -1.21 g /cm 3 ). The CT had a bulk density ranged between 1.13 and 1.30 g/cm 3 . With a RCT tillage, the bulk density during the growing season of rape was located in optimal density zone between 1.20 and 1.22 g/cm 3 . The RCT of rapeseed provided the greatest efficiency, where the yield of rapeseed increased by 13.3% and 22.0%. It has been revealed that with RCT of rapeseed cultivation, minimum technology (Mini-till) ensures sustainability of soil environment and its ecological condition, improves structure and raises water resistance of agroecosystem’s soil aggregate. In turn the structure of soil’s arable layer stabilizes with optimal soil density, which contributes to normal growth and development of rapeseed. It is proved that minimal technology of tillage is the leading agricultural practice ensuring preservation and improvement of qualitative and quantitative indicators of soil resource and productivity of oilseed rape.

Improving Water Use Efficiency under Deficit Irrigation in the Jordan Valley

The Jordan Valley is the prime irrigated agricultural area in Jordan which suffers shortage of water putting severe limitation on water allocation to farmers. To alleviate the problem, deficit irrigation was proposed for some vegetables such as bell pepper. Two field experiments in two growing seasons were conducted using bell pepper (Capsicum Annuum L.) to assess the effect of deficit irrigation on yield, water use efficiency (WUE), and water productivity (WP). The treatments were three irrigation levels: 100% (T1), 80% (T2), and 60% (T3) of the calculated crop evapotranspiration (ETc) using class A pan method. A cost–benefit analysis was carried out to determine the best economically suitable season for crop growth. The yields in both seasons were higher under T1, but there was no difference in WUE and WP between T1 and T2. The yield, WUE, and WP for T3 were significantly lower than for T1 and T2. Therefore, it is recommended to irrigate at 80% of ET. The best results were obtained for the total gross margin and the net present value in the winter season. Using deficit irrigation reduces water usage without significant yield loss, meanwhile maintaining relatively high WUE and supporting the sustainability of agriculture in the Jordan Valley.

Tempo‐spatial land use/cover change in Zeway, Ketar and Bulbula sub‐basins, Central Rift Valley of Ethiopia

AbstractUnderstanding tempo‐spatial dynamics of land‐use/cover (LULC) and its drivers is instrumental in synthesizing knowledge for informed natural resource management planning and associated decisions. The present study investigates tempo‐spatial LULC changes, their drivers and the associated impacts in three sub‐basins (Zeway, Ketar and Bulbula) in the Central Rift Valley (CRV) of Ethiopia. Satellite imageries of different periods in ArcGIS, field observations, focus group discussions (FGDs) and secondary data were used to analyse the LULC dynamics, their drivers and associated impacts from 1973 to 2014. The overall accuracy of 1973, 2003 and 2014 classification maps was 88.7%, 88.9% and 91.6%, respectively. The analysis results revealed a continuous increase of farmland and town built‐up areas at the expense of grasslands, shrub‐bush land and woodlands. It further indicated area of open irrigated agriculture, increasing from none to 2.61% of the total area. The FGDs demonstrated agricultural land expansion, resettlement and wood extraction were proximate causes of the observed LULC changes. Population increases, changes in land tenure system and decreased farmland productivity were determined to be the underlying causes of the changes. The FGDs further indicated these changes have negatively affected the natural resources. The present study findings indicate the need to reconsider land‐use decision tradeoffs between economic, social and environmental demands, and their implications for other similar areas in Ethiopia and beyond. Quantitative analysis and periodic evaluation of the drivers of such change and the impacts of existing and emerging land‐uses in the face of changing climate is recommended to facilitate sustainable use of the fragile ecosystems in the Ethiopian CRV.

Impact of agricultural water-saving practices on regional evapotranspiration: The role of groundwater in sustainable agriculture in arid and semi-arid areas

Evapotranspiration (ET) is an important component of the water budget process and is characterized by complex spatiotemporal changes, especially in irrigated agricultural areas. The impact of various hydrological processes and human activities on ET is still a meaty theme to study and investigate. A typical agricultural irrigation district with shallow groundwater and arid climate conditions was selected as the case study area in this work. The impact of the supplied irrigation water, shallow groundwater, crop planting pattern, and weather conditions on regional ET was determined after the regional ET was estimated by a Surface Energy Balance Algorithm of Land (SEBAL) model with Moderate Resolution Imaging Spectroratiometer (MODIS) data. The results show that the regional ET in Hetao kept declining in the past 15 years. The positive correlation between the water input (water diversion and precipitation) and ET indicated that reduced water diversion controls the declining ET, also causing the drop of groundwater level. Due to capillary forces and root uptake, the shallow groundwater tended to move upward to support the crop water consumption because the soil suffered from a water deficit. Furthermore, we quantified the contribution of shallow groundwater to regional ET and found that the water supplied from shallow groundwater increased from 5% to 15% during the period of water–saving irrigation. However, the long–term decrease of irrigation water supply and groundwater level caused a soil water deficit over the crop growth period, and the variation of crop planting pattern reduced ET as well. Therefore, groundwater plays an important role in sustainable agricultural development in arid and semiarid areas and the contribution of shallow groundwater to regional water consumption cannot be neglected.

Prediction of land use changes based on Land Change Modeler and attribution of changes in the water balance of Ganga basin to land use change using the SWAT model

Conflicts between increasing irrigated agricultural area, commercial crops, shifting cultivation and ever increasing domestic and industrial demand has already been a cause of tension in the society over water in the Ganga River Basin, India. For the development of sustainable water resource strategies, it is essential to establish interaction between landuse changes and local hydrology through proper assessment. Precisely, seeing how change in each LULC affects hydrologic regimes, or conversely evaluating which LULC shall be appropriate for the local hydrological regime can help decision makers to incorporate in the policy instruments. In this study, hydrologic regimes of the Ganga River basin have been assessed with landuse change. Catchment hydrologic responses were simulated using Soil and Water Assessment Tool (SWAT). Meteorological data from IMD of 0.25° × 0.25° spatial resolution were taken as the climate inputs. Simulated stream flow was compared at different gauge stations distributed across the Gang River and its tributaries. Urbanization has been the topmost contributor to the increase in surface runoff and water yield. While increased irrigation demands were the dominant contributor to the water consumption and also added to the increased evapotranspiration. This study can be important tool in quantifying the changes in hydrological components in response to changes made in landuse in especially basins undergoing rapid commercialization. This shall provide substantive information to the decision makers required to develop ameliorative strategies.

Quantification of nitrate sources and fates in rivers in an irrigated agricultural area using environmental isotopes and a Bayesian isotope mixing model

Nitrate (NO3−) pollution in rivers caused by intensive human activities is becoming a serious problem in irrigated agricultural areas. To identify NO3− sources and reveal the impact of irrigation projects on NO3− pollution in rivers, the hydrochemistry and isotopes of irrigation water from the Yellow River (IW) and river water (RW), and potential source samples were analyzed. The mean NO3− concentrations in the IW and RW were 24.4 mg/L and 49.9 mg/L, respectively. Approximately 45.2% of RW samples (n = 31) exceeded the Chinese drinking water standard for NO3− (45 mg/L). The δ15N and δ18O values, combined with the Cl−/Na+, SO42−/Ca2+ ratio distributions, indicate that the NO3− in the RW mainly originated from chemical fertilizers, manure and sewage. A Bayesian model showed that manure and sewage contributed the most to the overall NO3− levels of the IW. In the RW, chemical fertilizers and IW contributed the most to the overall NO3− levels. The mean nitrate contribution to the RW from the combination of chemical fertilizers and IW is estimated to be 51.6%. Nitrogen from manure and sewage, soil N and precipitation also contributed. The NO3− pollution in rivers was largely influenced by the irrigation regime, with a large amount of nitrogen in chemical fertilizer lost because of low utilization efficiency and subsequent transfer, via irrigation runoff, into the rivers. This study suggests that with a detailed assessment of the sources and fate of NO3−, effective reduction strategies and better management practices can be implemented to control NO3− pollution in rivers.

Remote sensing techniques to predict salinity intrusion: application for a data-poor area of the coastal Mekong Delta, Vietnam

ABSTRACTSalinity intrusion is a complex issue in coastal and estuarine areas. Currently, remote sensing techniques have been widely used to monitor water quality changes, ranging from inland river networks to deep oceans. The Vietnamese Mekong Delta is an important rice-growing area, and intrusion of saline water into irrigated freshwater-based agriculture areas is one of the most crucial constraints for agriculture development. This study aimed at building a numerical model to realize the salinity intrusion through the relationship between reflectance from the Landsat-8 Operational Land Imager images and salinity levels measured in situ. A total of 103 observed samples were divided into 50% training and 50% test. Multiple Linear Regression, Decision Trees and Random Forest (RF) approaches were applied in the study. The result showed that the RF approach was the best model to estimate salinity along the coastal river network in the study area. However, the large samples size needed was a significant challenge to circumscribe predicting ability of the RF model. The reflectance has a good correlation with salinity when locations (latitude–longitude) of salinity measured stations were added as a parameter of the Step-wise model with R-square 77.48% in training and 74.16% in test while Root Mean Square Error was smaller than 3.

Influence of long-term donor irrigation on quality of underground water in the south-steppe zone of Ukraine (case of the Baraboy River, Odessa Region)

The article presents the results of in-situ studies of the chemical composition and quality of underground (subsoil and artesian) water within the basin of the Baraboy River where irrigation of agricultural areas using the water resources of the Dniester River has been carried out since 1967. These water resources are fed into the network of reservoirs and channels of the Lower Dniester Irrigation System. Filtration losses of water from irrigation areas and water supply and sewage systems of settlements replenish the reserves of underground (subsoil) waters increasing the ingress therein of dissolved substances from the sedimentary rocks which leads to increase in the concentrations of certain ingredients included in chemical composition of surface and underground waters within the basin of the Baraboy River. It is shown that groundwater is enriched with nitro-gen compounds containing high concentrations of chlorides, sulfates, calcium and magnesium. Mineralization, toxicity and degree of contamination of underground water increase along the length of the Baraboy River. The chemical composition of the groundwater coming to the riverbed of the Baraboy River does not meet the fishing requirements and worsen the water quality of fish farming water bodies. The results of assessment of groundwater quality at the stations under study give reason to consider these sources of groundwater as an important factor affecting the hydrochemical regime and the quality of the water of the Baraboy River and its reservoirs which should be taken into account when developing the recommendations for optimization of the current hydroecological state of the Baraboy River as a whole. If high mineralization and significant content of principle ions in groundwater can be explained by natural factors, the high level of contamination by biogenic substances is resulted from entering of industrial, domestic and return waters from irrigated areas into aquifers. Such contamination is not a temporary but a permanent phenomenon. In terms of magnesium content artesian waters used for utility and drinking water supply are recognized as «mediocre, suitable with limitations and having undesirable quality». In addition, after 50 years of operation compounds of nitrogen and phosphorus were found in artesian water, and this was not a case in 1960s of the last century. A conclusion on the negative effect of long-term donor irrigation on the quality of underground water and on the need for additional treatment of water of artesian aquifers of the Sarmatian Stage used for centralized water supply was made.